northd: Support an option to ignore chassis features.

Add option ignore_chassis_features for northd to bypass the support
status of features on each chassis and to directly implement the latest
features.

This is particularly useful for users who follow the suggested upgrade
order that upgrades ovn-controllers before ovn-northd, and want to
safeguard the operation of northd from being adversely affected by a
mismatched configuration of a chassis. This not only avoids feature
degradation but can also avoid risks of any broken feature in backward
compatible mode. An example of such impact is discussed at [0].

[0] https://mail.openvswitch.org/pipermail/ovs-dev/2023-September/407756.html

Signed-off-by: Han Zhou <hzhou@ovn.org>
Acked-by: Ales Musil <amusil@redhat.com>

northd/northd.c

@@ -17058,6 +17058,17 @@ destroy_datapaths_and_ports(struct ovn_datapaths *ls_datapaths,
     ovn_datapaths_destroy(lr_datapaths);
 }
 
+static void
+northd_enable_all_features(struct northd_data *data)
+{
+    data->features = (struct chassis_features) {
+        .ct_no_masked_label = true,
+        .mac_binding_timestamp = true,
+        .ct_lb_related = true,
+        .fdb_timestamp = true,
+    };
+}
+
 void
 northd_init(struct northd_data *data)
 {
@@ -17068,12 +17079,7 @@ northd_init(struct northd_data *data)
     hmap_init(&data->lbs);
     hmap_init(&data->lb_groups);
     ovs_list_init(&data->lr_list);
-    data->features = (struct chassis_features) {
-        .ct_no_masked_label = true,
-        .mac_binding_timestamp = true,
-        .ct_lb_related = true,
-        .fdb_timestamp = true,
-    };
+    northd_enable_all_features(data);
     data->ovn_internal_version_changed = false;
     sset_init(&data->svc_monitor_lsps);
     data->change_tracked = false;
@@ -17192,7 +17198,12 @@ ovnnb_db_run(struct northd_input *input_data,
                                               false);
     use_common_zone = smap_get_bool(&nb->options, "use_common_zone", false);
 
-    build_chassis_features(input_data->sbrec_chassis_table, &data->features);
+    if (smap_get_bool(&nb->options, "ignore_chassis_features", false)) {
+        northd_enable_all_features(data);
+    } else {
+        build_chassis_features(input_data->sbrec_chassis_table,
+                               &data->features);
+    }
 
     init_debug_config(nb);
 

ovn-nb.xml

@@ -157,6 +157,29 @@
         </column>
       </group>
 
+       <column name="options" key="ignore_chassis_features">
+        <p>
+          When set to <code>false</code>, the <code>ovn-northd</code> will
+          evaluate the features supported by each chassis and will only
+          activate features that are universally supported by all chassis. This
+          approach is crucial for maintaining backward compatibility during an
+          upgrade when the <code>ovn-northd</code> is updated prior to the
+          <code>ovn-controller</code>. However, if any chassis is poorly
+          managed and the upgrade is unsuccessful, it will restrict
+          <code>ovn-northd</code> from activating the new features.
+        </p>
+        <p>
+          Alternatively, setting this option to <code>true</code> instructs
+          <code>ovn-northd</code> to bypass the support status of features on
+          each chassis and to directly implement the latest features. This
+          approach safeguards the operation of <code>ovn-northd</code> from
+          being adversely affected by a mismatched configuration of a chassis.
+        </p>
+        <p>
+          The default setting for this option is <code>false</code>.
+        </p>
+      </column>
+
       <column name="options" key="mac_prefix">
         Configure a given OUI to be used as prefix when L2 address is
         dynamically assigned, e.g. <code>00:11:22</code>